JP6436131B2 - Toner for electrostatic latent image development - Google Patents

Description

  The present invention relates to an electrostatic latent image developing toner.

  In Patent Document 1, the amount of silica released from a toner after being subjected to high-temperature and high-humidity environmental stress is not greatly reduced relative to the amount of silica released from the toner before being subjected to high-temperature and high-humidity environmental stress A technique for adjusting to the above is disclosed.

JP 2014-178528 A

  However, it is difficult to obtain a toner having sufficient durability, chargeability, and cleaning properties that can withstand continuous printing only by the technique disclosed in Patent Document 1.

  The present invention has been made in view of the above problems, and provides an electrostatic latent image developing toner capable of continuously forming high-quality images over a long period of time even when used for continuous printing. For the purpose.

The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles including toner base particles and an external additive attached to the surface of the toner base particles. The toner particles include silica particles and resin particles as the external additive. The resin particles are substantially composed of a styrene-acrylic acid resin. The toner base particles include a core containing a binder resin and a release agent, and a shell layer that covers the surface of the core. The shell layer covers an area of 60% to 80% of the surface area of the core. The amount of the silica particles is 1.0 to 2.0 parts by mass with respect to 100 parts by mass of the toner base particles, and the amount of the resin particles is 0.5 to 2.0 parts by mass. It is. In the range from the surface of the toner particle to a depth of 1 nm, the number of fragment ions derived from the release agent measured by quantitative analysis by time-of-flight secondary ion mass spectrometry is the count of all positive ions. It is 1000 ppm or more and 2000 ppm or less with respect to the number. The silica liberation rate of the toner measured after the airflow classification process under the conditions of a toner supply amount of 100 g / min, a rotation speed of 12000 rpm, and a blower air volume of 6 m ³ / min is 3.0% or more and 5.0% or less.

  According to the present invention, it is possible to provide an electrostatic latent image developing toner capable of continuously forming a high-quality image over a long period of time even when used for continuous printing.

  An embodiment of the present invention will be described. Note that the evaluation results (values indicating the shape or physical properties) of the powder (more specifically, the toner core, toner base particles, external additive, toner, etc.) are averaged from the powder unless otherwise specified. This is the number average of the values measured for each of the average particles by selecting a significant number of such particles.

The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. . Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is not specified, and the “Coulter Counter Multisizer 3” manufactured by Beckman Coulter Co., Ltd. is used. ) Measured based on.

  The glass transition point (Tg) is a value measured according to “JIS (Japanese Industrial Standard) K7121-2012” using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. It is. In the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) at the second temperature rise measured by the differential scanning calorimeter, the change point of the specific heat (outside the extrapolated line of the baseline and the falling line) The temperature (onset temperature) at the intersection with the insertion line corresponds to Tg (glass transition point). Moreover, the softening point (Tm) is a value measured using a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation) unless otherwise specified. In the S curve (horizontal axis: temperature, vertical axis: stroke) measured with the Koka type flow tester, the temperature that becomes "(baseline stroke value + maximum stroke value) / 2" is Tm (softening point). Equivalent to. Moreover, each measured value of a number average molecular weight (Mn) and a mass average molecular weight (Mw) is the value measured using the gel permeation chromatography, if not prescribed | regulated at all.

  The chargeability means the chargeability in frictional charging unless otherwise specified. The strength of positive chargeability (or strength of negative chargeability) in frictional charging can be confirmed by a known charge train or the like.

Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. Further, acrylonitrile (CH ₂ ═CHCN) and methacrylonitrile (CH ₂ ═C (CH ₃ ) CN) may be collectively referred to as “(meth) acrylonitrile”. The crystalline polyester resin is described as “crystalline polyester resin”, and the non-crystalline polyester resin is simply described as “polyester resin”.

  The toner according to the exemplary embodiment can be suitably used for developing an electrostatic latent image, for example, as a positively chargeable toner. The toner of the present exemplary embodiment is a powder that includes a plurality of toner particles (each having a configuration described later). The toner may be used as a one-component developer. Further, a two-component developer may be prepared by mixing a toner and a carrier using a mixing device (more specifically, a ball mill or the like). In order to form a high-quality image, it is preferable to use a ferrite carrier as a carrier. In order to form a high-quality image over a long period of time, it is preferable to use magnetic carrier particles including a carrier core and a resin layer covering the carrier core. In order to impart magnetism to the carrier particles, the carrier particles may be formed of a magnetic material, or the carrier particles may be formed of a resin in which the magnetic particles are dispersed. Further, magnetic particles may be dispersed in the resin layer covering the carrier core. In order to form a high-quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier. The positively chargeable toner is positively charged by friction with the carrier.

  The toner according to the exemplary embodiment can be used for image formation in, for example, an electrophotographic apparatus (image forming apparatus). Hereinafter, an example of an image forming method using an electrophotographic apparatus will be described.

  First, an electrostatic latent image is formed on a photoconductor (for example, a surface layer portion of a photoconductor drum) based on image data. Next, the formed electrostatic latent image is developed using a developer containing toner. In the developing process, toner (toner charged by friction with a carrier or blade) on a developing sleeve (for example, a surface layer of a developing roller in the developing device) disposed in the vicinity of the photosensitive member is attached to the electrostatic latent image. Thus, a toner image is formed on the photoreceptor. In the subsequent transfer step, the toner image is transferred to an intermediate transfer member (for example, a transfer belt), and then the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta, and cyan. Note that the toner remaining on the photoreceptor after the transfer step is removed by cleaning. For example, in a blade cleaning type photosensitive drum, the surface of the photosensitive member is rubbed with an edge portion of a cleaning blade (for example, a rubber blade) to scrape and remove residual toner on the photosensitive member.

  The toner according to the exemplary embodiment is an electrostatic latent image developing toner having the following configuration (hereinafter referred to as a basic configuration).

(Basic toner configuration)
The toner includes a plurality of toner particles including toner mother particles and an external additive attached to the surface of the toner mother particles. The toner particles include silica particles and resin particles as external additives. The resin particles are substantially composed of a styrene-acrylic acid resin. The toner base particles include a toner core and a shell layer that covers the surface of the toner core. The toner core contains a binder resin and a release agent. The shell layer covers an area of 60% to 80% of the surface area of the toner core. The amount of silica particles is 1.0 to 2.0 parts by mass and the amount of resin particles is 0.5 to 2.0 parts by mass with respect to 100 parts by mass of toner base particles. In the range from the surface of the toner particle to a depth of 1 nm, the release agent (on the toner core) is measured by quantitative analysis by Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The count number of fragment ions derived from the contained release agent is 1000 ppm or more and 2000 ppm or less with respect to the count number of all positive ions. The silica liberation rate of the toner measured after the airflow classification process under the conditions of a toner supply amount of 100 g / min, a rotation speed of 12000 rpm, and a blower air volume of 6 m ³ / min is 3.0% or more and 5.0% or less.

  Silica particles released from toner particles (hereinafter referred to as free silica particles) include silica particles that are completely detached from toner particles and silica particles that are present on the surface of toner particles in a state of being released from toner particles. included. Silica particles present on the surface of the toner particles in a state free from the toner particles are lightly adhered to the surface of the toner particles. Since these silica particles are not integrated with the toner particles, they are easily separated from the toner particles. On the other hand, the silica particles fixed to the surface of the toner particles are not released from the toner particles.

  By including a certain amount of free silica particles in the toner, the developability and heat-resistant storage stability of the toner can be improved (see Tables 1 to 3 below). However, when the amount of the free silica particles is too large, the toner or the external additive is fixed to the developing sleeve (hereinafter referred to as sleeve fixing) easily. In the toner having the above basic configuration, the silica liberation rate (ratio of free silica particles in the silica particles in the toner) becomes an appropriate size, so that sufficient toner development is achieved while suppressing the sticking of the sleeve in continuous printing. Property and heat-resistant storage stability are easily secured.

  As the amount of the release agent present in the surface layer portion of the toner particles increases, the count number defined by the above basic configuration (specifically, the count number of the fragment ions derived from the release agent measured by TOF-SIMS) increases. Tend to be. If the amount of the release agent present in the surface layer portion of the toner particles is too large, sleeve fixation tends to occur when continuous printing with a high printing rate (for example, a printing rate of 10%) is performed using toner. In addition, when the amount of the release agent present on the surface layer portion of the toner particles is too small, the slipping property between the photosensitive drum (image carrier) and the cleaning blade is lowered, and the cleaning blade is turned up (hereinafter referred to as “cleaning blade”). , Described as turning the blade). Further, when the amount of the release agent present on the surface layer portion of the toner particles is too small, the fluidity of the toner is lowered and the charge amount of the toner tends to be insufficient. In the toner having the above basic configuration, the amount of the release agent present on the surface layer portion of the toner particles becomes an appropriate amount, so that it is easy to ensure a sufficient toner charge amount while suppressing sleeve sticking and blade turning in continuous printing. Become.

  In TOF-SIMS, image-mapped data (image data) can be easily acquired. For this reason, by analyzing the surface of the toner particle by TOF-SIMS, the type of molecule present at each position on the surface of the toner particle and the abundance of the molecule can be easily measured.

  In order to achieve both the durability and the fixing property of the toner, the shell layer preferably covers an area of 60% to 80% of the surface area of the toner core. Hereinafter, the area covered by the shell layer in the surface area of the toner core is referred to as a shell covering area. In addition, the ratio of the shell covering area to the surface area of the toner core is referred to as a shell covering ratio. The shell coverage is expressed by the formula “shell coverage (unit:%) = 100 × area of shell coating area / area of toner core surface area”.

  In order to ensure sufficient chargeability and durability of the toner while suppressing the sticking of the sleeve in continuous printing, in the above basic configuration, the amount of silica particles is 1.0 part by mass with respect to 100 parts by mass of toner base particles. The amount of resin particles (specifically, particles substantially composed of a styrene-acrylic acid resin) is 0.5 parts by mass or more and 2.0 parts by mass or less. preferable. By including a certain amount of silica particles in the toner, the fluidity of the toner can be improved. In addition, by including a certain amount of the resin particles in the toner, it is possible to suppress the occurrence of reversely charged toner (and hence the occurrence of fogging). If the amount of silica particles is too small, the durability of the toner tends to be insufficient. When the amount of silica particles is too large, the charging stability of the toner tends to be insufficient. If the amount of the resin particles is too small, the charge amount and charge stability of the toner tend to be insufficient. On the other hand, when the amount of the resin particles is too large, sleeve sticking is likely to occur when continuous printing is performed with a toner at a high printing rate (for example, a printing rate of 10%).

  In order to continuously form high-quality images in continuous printing, the number average primary particle diameter of silica particles is 0.01 μm or more and 0.10 μm or less, and the number average primary particle diameter of resin particles is 0.00. It is preferable that it is 05 μm or more and 0.20 μm or less. If the number average primary particle diameter of the silica particles is too small, the silica liberation rate of the toner tends to be small. If the number average primary particle diameter of the silica particles is too large, the silica liberation rate of the toner tends to increase. If the resin particles are too small, the chargeability of the toner tends to deteriorate. If the resin particles are too large, the low-temperature fixability of the toner tends to deteriorate.

  In order for the toner to have the above basic configuration, the toner core is preferably a pulverized core prepared by a pulverization method (a kind of dry method). The pulverization method is a method of obtaining a powder (for example, a toner core) through a step of obtaining a kneaded product by melting and kneading a plurality of types of materials (resins and the like) and a step of pulverizing the obtained kneaded product.

  In order to achieve both the durability and the fixing property of the toner, the thickness of the shell layer is preferably 30 nm or more and 60 nm or less. The thickness of the shell layer can be measured by analyzing a TEM (transmission electron microscope) image of the cross section of the toner particles using commercially available image analysis software (for example, “WinROOF” manufactured by Mitani Corporation). If the thickness of the shell layer is not uniform in one toner particle, four equally spaced locations (specifically, two straight lines that are perpendicular to each other at the approximate center of the cross section of the toner particle are drawn. The thickness of the shell layer is measured at each of the four points where the straight line intersects the shell layer, and the arithmetic average of the four measured values obtained is taken as the evaluation value of the toner particles (shell layer thickness). When the boundary between the toner core and the shell layer is unclear in the TEM image, a combination of TEM and electron energy loss spectroscopy (EELS) is used to combine the characteristics included in the shell layer in the TEM image. By mapping various elements, the boundary between the toner core and the shell layer can be clarified.

In order to obtain a toner suitable for image formation, the volume median diameter (D ₅₀ ) of the toner core is preferably 1 μm or more and less than 10 μm.

  Resins suitable for forming toner particles are as follows.

<Preferable thermoplastic resin>
Suitable examples of thermoplastic resins include styrene resins, acrylic resins (more specifically, acrylic ester polymers or methacrylic ester polymers), olefin resins (more specifically, polyethylene). Resin or polypropylene resin), vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, N-vinyl resin, polyester resin, polyamide resin, or urethane resin. Further, a copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the resin (specifically, a styrene-acrylic acid resin or a styrene-butadiene resin) is used. May be.

  The thermoplastic resin can be obtained by addition polymerization, copolymerization, or condensation polymerization of one or more thermoplastic monomers. The thermoplastic monomer is a monomer that becomes a thermoplastic resin by homopolymerization (more specifically, an acrylic acid monomer or a styrene monomer), or a monomer that becomes a thermoplastic resin by condensation polymerization (for example, by condensation polymerization). A combination of a polyhydric alcohol and a polyhydric carboxylic acid to be a polyester resin.

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. In order to synthesize a styrene-acrylic acid resin, for example, a styrene monomer and an acrylic acid monomer as shown below can be suitably used.

  Preferable examples of the styrene monomer include styrene, alkyl styrene (more specifically, α-methyl styrene, p-ethyl styrene, 4-tert-butyl styrene, etc.), p-hydroxy styrene, m-hydroxy styrene. , Vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, or p-chlorostyrene.

  Preferable examples of the acrylic acid monomer include (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Suitable examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic. Examples include n-butyl acid, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Suitable examples of the (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or (meth) acrylic. The acid 4-hydroxybutyl is mentioned.

  The polyester resin is obtained by polycondensation of one or more polyhydric alcohols and one or more polyhydric carboxylic acids. As the alcohol for synthesizing the polyester resin, for example, dihydric alcohols (more specifically, diols or bisphenols) as shown below or trihydric or higher alcohols can be suitably used. As the carboxylic acid for synthesizing the polyester resin, for example, divalent carboxylic acids or trivalent or higher carboxylic acids as shown below can be suitably used.

  Preferable examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4. -Diol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

  Preferable examples of the bisphenol include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

  Preferable examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, or 1,3,5- Trihydroxymethylbenzene is mentioned.

  As preferable examples of the divalent carboxylic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid Succinic acid, alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, etc.), or alkenyl succinic acid (more specific Specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isododecenyl succinic acid, etc.) may be mentioned.

  Preferred examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) Examples include methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid.

<Preferable thermosetting resin>
Preferred examples of the thermosetting resin include melamine resin, urea resin, sulfonamide resin, glyoxal resin, guanamine resin, aniline resin, polyimide resin (more specifically, maleimide polymer or bismuth resin). Maleimide polymer, etc.) or xylene-based resins.

The thermosetting resin can be obtained by crosslinking (polymerizing) one or more thermosetting monomers. Moreover, a thermosetting resin can also be synthesize | combined with a thermoplastic monomer by using a crosslinking agent. The thermosetting monomer is a monomer having crosslinkability. For example, when monomers of the same kind are three-dimensionally connected via “—CH ₂ —” to become a thermosetting resin, the monomer corresponds to a “thermosetting monomer”.

  Preferable examples of the thermosetting monomer include methylol melamine, melamine, methylolated urea (more specifically, dimethylol dihydroxyethylene urea), urea, benzoguanamine, acetoguanamine, or spiroguanamine.

  Hereinafter, the toner core (binder resin and internal additive), shell layer, and external additive will be described in order. Depending on the use of the toner, unnecessary components (for example, internal additives) may be omitted.

[Toner core]
(Binder resin)
In the toner core, the binder resin generally occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner core. By using a combination of a plurality of types of resins as the binder resin, the properties of the binder resin (more specifically, the hydroxyl value, acid value, Tg, Tm, etc.) can be adjusted. For example, when the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core tends to become anionic, and the binder resin has an amino group or an amide group. The toner core tends to become cationic.

  In order to improve the low-temperature fixability of the toner, the toner core preferably contains a thermoplastic resin (more specifically, the “preferable thermoplastic resin” described above) as the binder resin. More preferably, the thermoplastic resin is contained in a proportion of 85% by mass or more of the entire resin. The toner core may contain a crystalline polyester resin as a binder resin. In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, it is preferable that 80% by mass or more of the resin contained in the toner core is a polyester resin.

  In order to improve toner fixability while ensuring sufficient toner core strength, the toner core preferably contains a plurality of types of polyester resins having different softening points (Tm) as the binder resin. It is particularly preferable to contain a polyester resin having a softening point of 75 ° C. or higher and a polyester resin having a softening point of 110 ° C. or higher. Further, when the toner core contains, as a binder resin, a polyester resin having a softening point of 70 ° C. or lower, a polyester resin having a softening point of 75 ° C. or higher and 100 ° C. or lower, and a polyester resin having a softening point of 110 ° C. or higher, sufficient In order to improve the toner fixability while ensuring the strength of the toner core, among the polyester resins contained in the toner core, a polyester resin having a softening point of 70 ° C. or lower is a polyester resin having a softening point of 70 ° C. or lower. Preferably there is.

  When a polyester resin is used as the binder resin for the toner core, the number average molecular weight (Mn) of the polyester resin is 1000 or more and 2000 or less in order to improve the toner fixing property while ensuring sufficient toner core strength. Is preferred. The molecular weight distribution of the polyester resin (the ratio Mw / Mn of the mass average molecular weight (Mw) to the number average molecular weight (Mn)) is preferably 9 or more and 21 or less.

(Coloring agent)
The toner core may contain a colorant. As the colorant, a known pigment or dye can be used according to the color of the toner. In order to form a high-quality image using toner, the amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner core may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner core may contain a color colorant such as a yellow colorant, a magenta colorant, or a cyan colorant.

  As the yellow colorant, for example, one or more compounds selected from the group consisting of condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds can be used. Examples of the yellow colorant include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191, or 194), naphthol yellow S, Hansa yellow G, or C.I. I. Vat yellow can be preferably used.

  The magenta colorant is, for example, selected from the group consisting of condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. One or more compounds can be used. Examples of the magenta colorant include C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254) can be preferably used.

  As the cyan colorant, for example, one or more compounds selected from the group consisting of a copper phthalocyanine compound, an anthraquinone compound, and a basic dye lake compound can be used. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, or 66), phthalocyanine blue, C.I. I. Bat Blue, or C.I. I. Acid blue can be preferably used.

(Release agent)
The release agent is used, for example, for the purpose of improving the fixing property or offset resistance of the toner. In order to achieve an appropriate amount of the release agent present on the surface layer portion of the toner particles, the amount of the release agent in the toner core (when using multiple types of release agents, the total amount of these release agents) ) Is preferably 4 parts by mass or more and 6 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxidized polyethylene wax or a block thereof Oxides of aliphatic hydrocarbon waxes such as copolymers; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax; animal properties such as beeswax, lanolin, or whale wax Waxes; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanate ester wax or castor wax; fats such as deoxidized carnauba wax The wax portion of the ester or the whole was deoxygenated can be suitably used. One type of release agent may be used alone, or multiple types of release agents may be used in combination.

  In order to improve the compatibility between the binder resin and the release agent, a compatibilizer may be added to the toner core.

(Charge control agent)
The toner core may contain a charge control agent. The charge control agent is used, for example, for the purpose of improving the charge stability or charge rising property of the toner. The charge rising characteristic of the toner is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

  By adding a negatively chargeable charge control agent (more specifically, an organometallic complex or a chelate compound) to the toner core, the anionicity of the toner core can be enhanced. Further, by adding a positively chargeable charge control agent (more specifically, pyridine, nigrosine, quaternary ammonium salt, or the like) to the toner core, the toner core can be made more cationic. However, if sufficient chargeability is ensured in the toner, it is not necessary to include a charge control agent in the toner core.

(Magnetic powder)
The toner core may contain magnetic powder. Examples of magnetic powder materials include ferromagnetic metals (more specifically, iron, cobalt, nickel, or alloys thereof), ferromagnetic metal oxides (more specifically, ferrite, magnetite, or dioxide). Chromium or the like) or a material subjected to a ferromagnetization treatment (more specifically, heat treatment or the like) can be preferably used. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

  In order to suppress elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to surface-treat the magnetic powder. When a shell layer is formed on the surface of the toner core under acidic conditions, if the metal ions are eluted on the surface of the toner core, the toner cores are easily fixed to each other. It is considered that fixing of the toner cores can be suppressed by suppressing elution of metal ions from the magnetic powder.

[Shell layer]
For example, the shell layer is bonded (chemically bonded) to the surface of the toner core by chemically reacting the toner core and the shell material (shell layer material) in the liquid. The shell layer may be a film without graininess or a film with graininess. When a shell layer is formed in an aqueous medium using a water-soluble material as the shell material, it is considered that a film having no graininess is formed as the shell layer. When resin particles are used as the shell material, it is considered that if the material (resin particles) is completely melted and cured in a film-like form, a film having no graininess is formed as the shell layer. On the other hand, if the material (resin particles) is not completely melted and cured in a film form, a film having a form in which the resin particles are two-dimensionally connected (a film having a granular feeling) is formed as a shell layer. it is conceivable that. For example, the resin particles are adhered to the surface of the toner core in the liquid and the liquid is heated, whereby the resin particles can be dissolved to form a film. However, the resin particles may be formed into a film by being heated in the drying step or receiving a physical impact force in the external addition step. The entire shell layer is not necessarily formed integrally. The shell layer may be a single film or an assembly of a plurality of films (islands) that are separated from each other.

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the shell layer preferably contains a thermoplastic resin (more specifically, the above-mentioned “preferable thermoplastic resin” or the like). Further, in order to improve the heat resistant storage stability of the toner, in addition to the thermoplastic resin, a thermosetting resin (more specifically, the above-mentioned “preferable thermosetting resin” or the like) is included in the shell layer. May be.

In order to improve the charging stability of the toner, the resin constituting the shell layer is preferably hydrophobic. In order for the resin to have sufficient hydrophobicity, the ratio of the repeating unit having a hydrophilic functional group among all the repeating units contained in the resin is preferably 10% by mass or less. The hydrophilic functional group is an acid group (more specifically, a carboxyl group or a sulfo group), a hydroxyl group, or a salt thereof (more specifically, —COONa, —SO ₃ Na, or —ONa). is there.

  In order to improve the charging stability of the toner, the shell layer is a co-polymerization of one or more styrene monomers (for example, styrene monomers) and one or more acrylic monomers (for example, acrylate monomers). It is particularly preferable to contain a coalescence. Styrene-acrylic acid resins are more hydrophobic than polyester resins and tend to be positively charged. Further, in order to uniformly cover the toner core with a shell layer having sufficient hydrophobicity, the resin contained in the shell layer is 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, Or it is preferable to have 1 or more types of alcoholic hydroxyl groups derived from 2-hydroxypropyl methacrylate, and it is particularly preferable that no hydrophilic functional groups other than these alcoholic hydroxyl groups are present.

[External additive]
An external additive (specifically, a powder containing a plurality of external additive particles) adheres to the surface of the toner base particles. Specifically, the toner particles include silica particles and resin particles (specifically, styrene-acrylic acid resin particles) as external additives. For example, the toner base particles (powder) and the external additive (powder) are stirred together, so that the external additive adheres (physically bonds) to the surface of the toner base particles with a physical force. The additive may be dispersed in the styrene-acrylic acid resin constituting the resin particles.

Hydrophobicity and / or positive chargeability may be imparted to the surface of the silica particles by the surface treatment agent. Examples of the surface treatment agent include a coupling agent (more specifically, a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent), or silicone oil (more specifically, dimethyl silicone oil). Etc.) can be suitably used. As the silane coupling agent, a silane compound (more specifically, methyltrimethoxysilane, aminosilane or the like) may be used, or a silazane compound (more specifically, HMDS (hexamethyldisilazane) or the like). May be used. When the surface of the silica particles is treated with the surface treatment agent, a large number of hydroxyl groups (—OH) present on the surface of the silica particles are partially or entirely substituted with functional groups derived from the surface treatment agent. As a result, silica particles having a functional group derived from the surface treating agent (specifically, a functional group that is more hydrophobic and / or positively charged than the hydroxyl group) on the surface can be obtained. For example, when the surface of the silica particles is treated with a silane coupling agent having an amino group, the hydroxyl group of the silane coupling agent (for example, a hydroxyl group generated by hydrolysis of the alkoxy group of the silane coupling agent with moisture) A dehydration condensation reaction (“A (silica particle) —OH” + “B (coupling agent) —OH” → “AO—B” + H ₂ O) occurs with a hydroxyl group present on the surface of the silica particle. By such a reaction, the amino group is imparted to the surface of the silica particle by chemically bonding the silane coupling agent having an amino group and the silica particle. More specifically, the hydroxyl group present on the surface of the silica particles is substituted with a functional group having an amino group at the end (more specifically, —O—Si— (CH ₂ ) ₃ —NH ₂ or the like). Silica particles provided with amino groups tend to have a stronger positive charge than untreated silica particles. When a silane coupling agent having an alkyl group is used, a hydroxyl group present on the surface of the silica particle is converted into a functional group having an alkyl group at the end (more specifically, − it can be replaced by O-Si-CH _3, etc.). Thus, the silica particle to which the hydrophobic group (alkyl group) was provided instead of the hydrophilic group (hydroxyl group) tends to have stronger hydrophobicity than the untreated silica particle.

[Toner Production Method]
Hereinafter, an example of a method for producing the toner according to the exemplary embodiment having the above configuration will be described.

(Preparation of toner core)
In order to easily obtain a suitable toner core, it is preferable to prepare the toner core by an aggregation method or a pulverization method. In addition, in order to easily and appropriately manufacture the toner having the above basic configuration, it is particularly preferable to prepare a toner core by a pulverization method.

  Hereinafter, an example of the pulverization method will be described. First, a binder resin and an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and magnetic powder) are mixed. Subsequently, the obtained mixture is melt-kneaded. Subsequently, the obtained melt-kneaded product is cooled. Subsequently, the cooled melt-kneaded product is pulverized and classified. As a result, a toner core having a desired particle size can be obtained.

  In order to easily and appropriately manufacture the toner having the above-described basic configuration, the toner core material (for example, the binder resin and the release agent) is melt-kneaded and then cooled by the following steps (melt-kneading step and It is preferable to go through a cooling step. In the melt-kneading step, the toner core material is supplied into a cylinder of a melt-kneading extruder, and the toner core material is melt-kneaded in the cylinder using the melt-kneading extruder to obtain a kneaded product. In the cooling step, the kneaded product is extruded from a melt-kneading extruder toward a cooling roll, and the kneaded product is cooled by passing it through a cooling roll having a temperature of 5 ° C. or higher and 9 ° C. or lower. By rapidly cooling the melt-kneaded material of the toner core material with a low-temperature cooling roll, it becomes easy to adjust the amount of the release agent present in the surface layer portion of the toner particles to an appropriate amount.

(Formation of shell layer)
First, an aqueous medium (for example, ion exchange water) is prepared. The aqueous medium is a medium containing water as a main component (more specifically, pure water or a mixed liquid of water and a polar medium). The aqueous medium may function as a solvent. A solute may be dissolved in the aqueous medium. The aqueous medium may function as a dispersion medium. The dispersoid may be dispersed in the aqueous medium. As a polar medium in the aqueous medium, for example, alcohol (more specifically, methanol or ethanol) can be used. The boiling point of the aqueous medium is about 100 ° C.

  Subsequently, the pH of the aqueous medium is adjusted to 3.0 or more and 6.0 or less using an acidic substance (for example, hydrochloric acid). Subsequently, a toner core and a shell material (for example, a suspension of resin particles) are added to an aqueous medium whose pH is adjusted (an acidic aqueous medium). As the addition amount of the shell material is increased, the thickness of the formed shell layer tends to increase. As the resin particles (shell material), for example, copolymer particles of one or more styrene monomers and one or more acrylic monomers can be used. In order to improve the film quality of the shell layer, the number average primary particle diameter of the resin particles (shell material) is preferably 30 nm or more and 60 nm or less.

  When the toner core and the shell material are added to the aqueous medium, it is considered that the shell material (for example, resin particles contained in the suspension) adheres to the surface of the toner core in the aqueous medium. In order to uniformly adhere the shell material to the surface of the toner core, it is preferable to highly disperse the toner core in a liquid containing the shell material. In order to highly disperse the toner core in the liquid, a surfactant may be included in the liquid, or the liquid is stirred using a powerful stirring device (for example, “Hibis Disper Mix” manufactured by Primics Co., Ltd.). May be. As the surfactant, for example, sulfate ester salt, sulfonate salt, phosphate ester salt, or soap can be used.

  Subsequently, while stirring the liquid containing the toner core and the shell material, the liquid temperature is set at a predetermined holding temperature (for example, a speed selected from 0.1 ° C./min to 3 ° C./min). The temperature is selected from 50 ° C to 85 ° C. Furthermore, the temperature of the liquid is maintained at the holding temperature for a predetermined time (for example, a time selected from 30 minutes to 4 hours) while stirring the liquid. It is considered that a chemical reaction (immobilization of the shell layer) proceeds between the toner core and the shell material while the temperature of the liquid is kept high (or during the temperature increase). The shell material is chemically bonded to the toner core to form a shell layer. For example, shell material particles (water-insoluble thermoplastic resin particles contained in a suspension) are melted by heat (or deformed) two-dimensionally on the surface of the toner core to form a film (shell) Layer) is formed.

  As described above, the resin particles are adhered to the surface of the toner core in the liquid, and the liquid is heated, whereby the resin particles can be dissolved (or deformed) to form a film. However, the resin particles may be formed into a film by being heated in the drying step or receiving a physical impact force in the external addition step.

  By forming a shell layer on the surface of the toner core in the liquid as described above, a dispersion of toner base particles can be obtained. Subsequently, the obtained dispersion of toner mother particles is filtered using, for example, a Buchner funnel. Thereby, the toner base particles are separated from the liquid (solid-liquid separation), and wet cake-like toner base particles are obtained. Subsequently, the obtained wet cake-like toner base particles are washed. Subsequently, the washed toner base particles are dried. Thereafter, if necessary, the toner base particles and external additives are mixed using a mixer (for example, FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.), and external additives (for example, Silica particles and resin particles) are adhered. When a spray dryer is used in the drying step, the drying step and the external addition step can be performed at the same time by spraying the dispersion of the external additive onto the toner base particles. In this way, a toner containing a large number of toner particles is obtained.

  The contents and order of the toner manufacturing method can be arbitrarily changed according to the required configuration or characteristics of the toner. For example, when reacting a material (for example, a shell material) in a liquid, the material may be reacted in the liquid for a predetermined time after the material is added to the liquid, or the material is added to the liquid over a long period of time. Then, the material may be reacted in the liquid while adding the material to the liquid. Moreover, a material (for example, shell material) may be added to the liquid at once, or may be added to the liquid in a plurality of times. The toner may be sieved after the external addition step. Further, unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using a commercially available product. Moreover, even if it does not adjust pH of a liquid, when reaction for forming a shell layer advances favorably, you may omit a pH adjustment process. As a material for synthesizing the resin, a prepolymer may be used instead of the monomer, if necessary. In order to obtain a predetermined compound, a salt, ester, hydrate, or anhydride of the compound may be used as a raw material. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously. The toner particles produced at the same time are considered to have substantially the same configuration.

  Examples of the present invention will be described. Table 1 shows toners TA-1 to TA-12 and TB-1 to TB-12 (each toner for developing an electrostatic latent image) according to Examples or Comparative Examples.

  Hereinafter, the production methods, evaluation methods, and evaluation results of the toners TA-1 to TA-12 and TB-1 to TB-12 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value. A transmission electron microscope (TEM) (“JSM-6700F” manufactured by JEOL Ltd.) was used for the measurement of the number average particle diameter.

[Production of toner]
(Production of toner core)
750 g of low viscosity polyester resin (Tg = 38 ° C., Tm = 65 ° C.), 100 g of medium viscosity polyester resin (Tg = 53 ° C., Tm = 84 ° C.), high viscosity polyester resin (Tg = 71 ° C., Tm = 120 ° C.) ) 150 g, 55 g of mold release agent (“Carnauba Wax No. 1” manufactured by Hiroyuki Kato, Carnauba Wax) and 40 g of colorant (“KET BLUE 111” manufactured by DIC Corporation, phthalocyanine blue) are mixed with an FM mixer ( Nippon Coke Kogyo Co., Ltd.) and mixed at a rotational speed of 2400 rpm.

  Subsequently, the resulting mixture was mixed with a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) at a material supply speed of 5 kg / hour, a shaft rotation speed of 160 rpm, and a set temperature range (cylinder temperature) of 80 ° C. or more. It was melt-kneaded under a condition of 110 ° C. or lower. The twin screw extruder (PCM-30) controls a cylinder, a hopper with a feeder (quantitative supply device) for supplying material into the cylinder, two screws arranged in the cylinder, and the cylinder temperature. With a heater for. Moreover, the sheet-like sheet | seat discharged | emitted from the twin-screw extruder (PCM-30) by arrange | positioning a cooling roll (accessory of "PCM-30" made by Ikegai Co., Ltd.) near the discharge port of a twin-screw extruder. The melt-kneaded material was conveyed by a belt conveyor and immediately passed through a cooling roll.

  Subsequently, the obtained melt-kneaded product was rolled and cooled through the cooling roll. The temperature of the cooling roll during cooling (when the melt-kneaded material passes) was set to a predetermined temperature (the temperature shown in Table 1 determined for each toner). For example, in the production of the toner TA-1, the temperature of the cooling roll was set to 7 ° C. The temperature of the cooling roll was controlled by controlling the temperature of the cooling water circulating in the cooling roll.

Subsequently, the cooled melt-kneaded product was coarsely pulverized using a pulverizer (“Rotoplex (registered trademark)” manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized product was finely pulverized under the conditions shown in Table 1 (blower air volume and outlet temperature) using a mechanical pulverizer (“Turbo Mill T250” manufactured by Freund Turbo). Subsequently, the obtained finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, a toner core having a volume median diameter (D ₅₀ ) of 6 μm was obtained.

(Preparation of suspension A)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath at a temperature of 30 ° C. Subsequently, 875 g of ion-exchanged water and 75 g of an anionic surfactant (“Latemul (registered trademark) WX” manufactured by Kao Corporation, component: sodium polyoxyethylene alkyl ether sulfate, solid content concentration: 26% by mass) are contained in the flask. And put. Thereafter, the temperature in the flask was raised to 80 ° C. using a water bath while stirring the contents of the flask. Subsequently, two kinds of liquids (first liquid and second liquid) were dropped into the flask over 5 hours while stirring the contents of the flask at 80 ° C. The first liquid was a mixed liquid of 14 g of styrene, 4 g of 2-hydroxyethyl methacrylate (HEMA), and 2 g of butyl acrylate. The second liquid was a solution in which 0.5 g of potassium persulfate was dissolved in 30 g of ion-exchanged water.

  Subsequently, while maintaining the temperature in the flask at 80 ° C., the flask contents were further stirred for 2 hours to sufficiently proceed the polymerization reaction of the flask contents. As a result, a suspension A (solid content concentration of 10% by mass) of resin fine particles (hydrophobic resin) was obtained. With respect to the resin particles contained in the obtained suspension A, the number average particle diameter was 38 nm. When the resin particles contained in the suspension A were put into tetrahydrofuran (THF), the resin particles swelled but did not dissolve.

(Preparation of suspension B)
The method for preparing the suspension B of resin fine particles (hydrophobic resin) (solid content concentration 10% by mass) is the same as the suspension except that the dropping time of each of the first liquid and the second liquid is changed from 5 hours to 7 hours. It was the same as the preparation method of A. Regarding the resin particles contained in the obtained suspension B, the number average particle diameter was 42 nm. When the resin particles contained in the suspension B were put into tetrahydrofuran (THF), the resin particles swelled but did not dissolve.

(Formation of shell layer)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was prepared. In the flask, 500 g of ion-exchanged water and sodium polyacrylate (“Jurimer (registered trademark) AC-103” manufactured by Toagosei Co., Ltd.) 50 g was added. As a result, a sodium polyacrylate aqueous solution was obtained in the flask.

  Subsequently, 100 g of the toner core produced by the above procedure was added to the flask. Subsequently, the contents of the flask were sufficiently stirred at room temperature (about 25 ° C.). As a result, a toner core dispersion was obtained in the flask.

  Subsequently, the obtained toner core dispersion was filtered using a filter paper having an opening of 3 μm to separate the toner core. Subsequently, the obtained toner core was redispersed in ion-exchanged water. Thereafter, filtration and dispersion were repeated 5 times to wash the toner core. Subsequently, 100 g of the toner core was dispersed in 500 g of ion-exchanged water in the flask to obtain a toner core suspension.

  Subsequently, 6.5 g of a shell material (suspension A or B shown in Table 1 defined for each toner) was added to the flask to obtain a suspension containing a toner core and a shell material. For example, in the production of toner TA-1, suspension A was used as the shell material. In the production of the toner TA-8, the suspension B was used as the shell material. Subsequently, dilute hydrochloric acid was added to the flask to adjust the pH of the suspension in the flask to 4.

  Subsequently, the suspension whose pH was adjusted to 4 was transferred to a 1 L separable flask equipped with a thermometer and a stirring blade, and the flask was set in a water bath. Subsequently, while stirring the flask contents at a rotation speed of 100 rpm, the flask contents were heated to a temperature of 65 ° C. at a rate of 1 ° C./min, and kept at that temperature (65 ° C.) for a predetermined holding time. The holding time was selected from a range of 10 minutes or more and 60 minutes or less so that the shell coverage becomes a value shown in Table 2 (for example, 70% for toner TA-1) for each toner. As the holding time is increased, the shell coverage tends to increase. At the start of heating, the temperature of the flask contents was 30 ° C.

  Subsequently, cold water was put into the flask, and the flask contents were rapidly cooled to room temperature (about 25 ° C.). As a result, a dispersion containing toner mother particles was obtained.

(Washing)
The dispersion of toner base particles obtained as described above was filtered (solid-liquid separation) using a Buchner funnel. As a result, toner base particles in the form of wet cake were obtained. Thereafter, the obtained wet cake-like toner base particles were redispersed in ion-exchanged water. Further, dispersion and filtration were repeated 5 times to wash the toner base particles.

(Dry)
Subsequently, the obtained toner base particles were dispersed in an aqueous ethanol solution having a concentration of 50% by mass. As a result, a slurry of toner base particles was obtained. Subsequently, the toner base particles in the slurry were removed under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min using a continuous surface reformer (“Coat Mizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.). Dried. As a result, dried toner base particles (powder) were obtained.

(External)
Using a 10 L FM mixer (manufactured by Nihon Coke Kogyo Co., Ltd.) having a temperature control jacket, 100 parts by weight of toner base particles prepared in the above-described procedure while circulating water at the temperature shown in Table 1 through the jacket And positively chargeable silica particles in the amount shown in Table 1 (silica particles imparted with positive charge by surface treatment: “AEROSIL (registered trademark) REA90” manufactured by Nippon Aerosil Co., Ltd., number average primary particle diameter: 20 nm) And resin particles in amounts shown in Table 1 ("Finesphere (registered trademark) FS-102" manufactured by Nippon Paint Industrial Coatings Co., Ltd.), component: non-crosslinked styrene-acrylic acid resin, number average primary particle diameter: 100 nm , Tg: 103 ° C., Tm: 225 ° C.) for 5 minutes at a rotational speed of 2400 rpm. It was deposited external additive (silica particles and resin particles) on the surface. For example, in the production of toner TA-1, 1.5 parts by mass of silica particles (AEROSIL REA90) and 1.0 part by mass of resin particles (Finesphere FS-102) are added to 100 parts by mass of toner base particles. They were mixed under the condition of a jacket temperature of 20 ° C. With respect to the external addition conditions of toner TA-1, the jacket temperature is changed from 20 ° C. to 10 ° C. in the external addition step of toner TB-5, and the jacket temperature is changed from 20 ° C. to 30 ° C. in the external addition step of toner TB-6. Changed to ° C. In the production of toner TA-9, 1.1 parts by mass of silica particles (AEROSIL REA90) and 1.0 part by mass of resin particles (Finesphere FS-102) are added to 100 parts by mass of toner base particles. They were mixed under the condition of a jacket temperature of 20 ° C.

  Thereafter, the obtained powder is sieved using a sieve of 200 mesh (aperture 75 μm), and toners (toner TA-1 to TA-12 and TB-1 to TB-12) containing a large number of toner particles are obtained. Obtained.

Regarding toners TA-1 to TA-12 and TB-1 to TB-12 obtained as described above, the amount of release agent present in the surface layer portion of the toner particles (unit: ppm), shell coverage (unit:%) ), And the silica liberation rate (unit:%) was measured by the following method. The measurement results are shown in Table 2. In the mass spectrum measured by TOF-SIMS, the amount of the release agent present in the surface layer portion of the toner particle is the count number of fragment ions derived from the release agent (I _A ) out of the count number (I _A ) of all positive ions. _B) corresponds to the ratio (= I _B / I _a) occupied. For example, in toner TA-1, the amount of the release agent present in the surface layer portion of the toner particles was 1550 ppm, the shell coverage was 70%, and the silica release rate was 4.1%. In each of toners TA-1 to TA-12 and TB-1 to TB-12, the thickness of the shell layer was 35 nm or more and 45 nm or less. The thickness of the shell layer was substantially the same as the particle size of the added suspension (shell material).

<Measurement method of shell coverage>
As a measuring device, an SPM probe station (“NanoNaviReal” manufactured by Hitachi High-Tech Science Co., Ltd.) provided with a scanning probe microscope (SPM) (“Multifunctional unit AFM5200S” manufactured by Hitachi High-Tech Science Co., Ltd.) was used. Prior to measurement, an average toner particle is selected from toner particles contained in a sample (toner) using a scanning electron microscope (SEM) (“JSM-6700F” manufactured by JEOL Ltd.), and the selected toner is selected. Particles were measured.

(SPM measurement conditions)
Measurement probe: low spring constant silicon cantilever ("OMCL-AC240TS-C3" manufactured by Olympus Corporation, spring constant: 2 N / m, resonance frequency: 70 kHz, back reflection coating material: aluminum)
・ Measurement mode: DFM (dynamic force mode)
・ Measurement range (one field of view): 1μm × 1μm
・ Resolution (X data / Y data): 256/256
・ Q gain: 1 × ・ Scanning frequency: 1 Hz

With the measurement mode (DFM), the toner particles are controlled while controlling the distance between the probe and the toner particles so that the amplitude of the vibrating cantilever becomes constant while the cantilever (tip portion: probe) is resonated. A shape image (image showing the surface shape) was obtained. The obtained shape image is analyzed using image analysis software (“WinROOF” manufactured by Mitani Corporation) and GIMP (GNU Image Manipulation Program: image editing / processing software distributed under the GNU General Public License). Then, the shell coating region (surface region of the toner core covered with the shell layer) was specified. Then, the shell coverage was calculated based on the formula “shell coverage (unit:%) = 100 × area of shell coating area / area of toner core surface area”. In each field of view, the area of the toner core surface area was 1 μm ² (area of measurement range). The shell coverage was measured at five locations while changing the field of view for one toner particle. Then, the arithmetic average value of the measured shell coverage at the five locations was used as the shell coverage of one toner particle as a measurement target. The shell coverage was measured for each of 10 toner particles contained in the sample (toner). The number average value of 10 toner particles was used as the evaluation value (shell coverage) of the sample (toner).

<Measurement method of silica release rate>
The sample (toner) was classified to remove free silica particles from the sample. Specifically, using a 100TTSP type classifier (manufactured by Hosokawa Micron Corporation), a sample (toner) airflow type classification process under the conditions of a sample supply rate of 100 g / min, a rotational speed of 12000 rpm, and a blower air volume of 6 m ³ / min Went.

  Before and after the classification treatment, the Si intensity (Net intensity) of the sample (toner) was measured by fluorescent X-ray analysis under the following conditions.

(Conditions for X-ray fluorescence analysis)
Analyzer: Scanning X-ray fluorescence analyzer (“ZSX” manufactured by Rigaku Corporation)
X-ray tube (X-ray source): Rh (Rhodium)
Excitation conditions: tube voltage 50 kV, tube current 50 mA
Measurement area (X-ray irradiation range): Diameter 30mm
Measuring element: Si (silicon)

Si intensity (Si _A ) before removal of free silica particles and Si intensity (Si _B ) after removal of free silica particles were measured by composition analysis of the toner using the fluorescent X-ray. Then, the silica liberation rate Si _x (unit:%) represented by the formula “Si _x = 100 × (Si _A −Si _B ) / Si _A ” was determined.

<Method for Measuring Amount of Release Agent in Surface Part of Toner Particle>
Using a time-of-flight secondary ion mass spectrometer (“IV type” manufactured by ION-TOF), primary ion species Bi ³⁺ , acceleration voltage 25 kV, irradiation current 0.1 pA, integration time 50 seconds, measurement range 100 μm The secondary ion mass spectrum of the toner particles contained in the sample (toner) under the conditions of × 100 μm (surface area: 100 μm square) and measurement depth of 1 nm (vertical axis: detection intensity (secondary ion count)), horizontal axis: Mass number (= mass / charge) was measured. Based on the obtained mass spectrum, the ratio (I _B ) of the count number (I _B ) of the fragment ions (mass number: 448) derived from the release agent out of all the measured counts (I _A ) of the positive ions ( = I _B / I _A ). For each of the ten toner particles contained in the sample (toner), as described above to measure the I _B ratio (= I _B / I _A), 10 measurements obtained in (I _B ratio) The arithmetic average value was taken as the evaluation value of the sample (toner) (the amount of release agent present in the surface layer portion of the toner particles).

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-12 and TB-1 to TB-12) is as follows.

(Heat resistant storage stability)
3 g of the sample (toner) was put in a 20 mL polyethylene container and sealed, and the sealed container was left in a thermostat set at 50 ° C. for 3 hours. Thereafter, the toner taken out from the thermostat was cooled to room temperature (about 25 ° C.) to obtain an evaluation toner.

Subsequently, the obtained toner for evaluation was placed on a sieve having an aperture of 150 μm with a known mass. Then, the mass of the sieve containing the toner for evaluation was measured, and the mass W1 of the toner before sieving was determined. Subsequently, the sieve was set in a powder tester (manufactured by Hosokawa Micron Corporation), and the sieve for evaluation was sieved by vibrating the sieve for 30 seconds under the condition of the rheostat scale 2 according to the manual of the powder tester. After sieving, the mass of the toner that did not pass through the sieve (the toner remaining on the sieve) (the mass W2 of the toner after sieving) was measured. Based on the mass W1 of the toner before sieving and the mass W2 of the toner after sieving, the toner passing rate W0 (unit: mass%) was determined according to the following formula.
W0 = 100 × (W1-W2) / W1

  When the toner passing rate is 80% by mass or more, it is evaluated as “good”, and when the toner passing rate is more than 60% by mass and less than 80% by mass, it is evaluated as Δ (normal), and the toner passing rate is 60% by mass or less. If so, it was evaluated as x (bad).

(Preparation of developer for evaluation)
100 parts by weight of a developer carrier (carrier for “FS-C5300DN” manufactured by Kyocera Document Solutions Co., Ltd.) and 10 parts by weight of a sample (toner) are mixed for 30 minutes using a ball mill, and an evaluation developer ( A two-component developer) was prepared.

(Preparation of evaluation machine)
A color printer (“FS-C5300DN” manufactured by Kyocera Document Solutions Inc.) was used as an evaluation machine. The evaluation developer prepared as described above was charged into the developing device of the evaluation machine, and the sample (replenishment toner) was charged into the toner container of the evaluation machine.

(Chargeability, charge stability)
Using the evaluation machine, continuous printing at a printing rate of 10% was performed on 10,000 sheets of paper (A4 size printing paper) in an environment of a temperature of 25 ° C. and a humidity of 50% RH. During continuous printing, from the start of printing up to 1000 sheets, every 200 sheets, and thereafter every 1000 sheets, using a Q / m meter ("MODEL 210HS-1" manufactured by Trek), the following evaluation method was used. The charge amount of the toner in the developing device was measured.

<Measurement method of charge amount of toner in developer>
0.10 g of developer (carrier and toner) was charged into a Q / m meter measurement cell, and only the toner out of the charged developer was sucked through a sieve (metal mesh) for 10 seconds. Then, based on the formula “total electric amount of sucked toner (unit: μC) / mass of sucked toner (unit: g)”, the charge amount of toner in the developer (unit: μC / g) is calculated. Calculated.

  Subsequently, based on the charge amount of the toner measured as described above, the arithmetic average value of the measured charge amount (hereinafter referred to as the average charge amount) and the width of the measured charge amount (hereinafter referred to as the average charge amount). And described as a difference in charge amount). The charge amount difference corresponds to the difference between the largest charge amount and the smallest charge amount measured during continuous printing.

  When the average charge amount was 20 μC / g or more and 30 μC / g or less, it was evaluated as “good”, and when the average charge amount was less than 20 μC / g or more than 30 μC / g, it was evaluated as “poor”. If the charge amount difference is 10 μC / g or less, it is evaluated as ◯ (good). If so, it was evaluated as x (bad).

(Developability)
Using the evaluation machine, continuous printing at a printing rate of 10% was performed on 100,000 sheets of paper (A4 size printing paper) in an environment of a temperature of 25 ° C. and a humidity of 50% RH. After continuous printing, a sample image including the solid part was printed on an evaluation sheet, and the image density (ID) of the solid part in the sample image was measured. For the measurement of image density, a reflection densitometer (“SpectroEye (registered trademark)” manufactured by X-Rite) was used. If the image density is 1.3 or more, it is evaluated as ◯ (good), if the image density is more than 1.1 and less than 1.3, it is evaluated as △ (normal), and if the image density is 1.1 or less. X (bad) was evaluated.

(Adhesion resistance)
Using the evaluation machine, continuous printing at a printing rate of 10% was performed on 100,000 sheets of paper (A4 size printing paper) in an environment of a temperature of 25 ° C. and a humidity of 50% RH. During continuous printing, the evaluation paper (“ColorCopy (registered trademark)” manufactured by Mondi, Inc. was used every 200 sheets up to 1000 sheets from the start of printing and every 1000 sheets thereafter, under the condition of a toner loading of 0.5 mg / cm ^2. , A4 size, 90 g / m ² ), an unfixed solid image was formed, and the formed solid image was visually observed. Further, the surface of the developing sleeve of the evaluator was visually observed. Then, the adhesion resistance of the sample (toner) was evaluated according to the following criteria.
○ (Good): Through the continuous printing of 100,000 sheets, coloring by the toner was not observed on the surface of the developing sleeve, and no image defect was observed in the solid image.
X (not good): At any timing during continuous printing of 100,000 sheets, coloring by the toner is observed on the surface of the developing sleeve, or image defects (for example, vertical stripes) are observed in the solid image. It was.

(Cleanability)
About the last printed paper after printing an evaluation image with a printing rate of 8% on 1000 sheets of paper (printing paper) continuously while cleaning the photosensitive drum by the blade cleaning method using the evaluation machine. The presence or absence of image stains (streaks, etc.) was visually determined. When the image stain was not confirmed, it was evaluated as ◯ (good), and when the image stain was confirmed, it was evaluated as x (bad). If the blade cleaning on the photosensitive drum is insufficient, a streak pattern may appear in the image due to toner slipping or the like.

[Evaluation results]
Table 3 shows the evaluation results of each sample (toners TA-1 to TA-12 and TB-1 to TB-12) (chargeability (average): average charge amount, chargeability (stable): charge amount difference, heat resistant storage. Property: toner passing rate, adhesion resistance: presence / absence of fixing of sleeve, cleaning property: presence / absence of cleaning failure, developability: image density).

The toners TA-1 to TA-12 (toners according to Examples 1 to 12) each had the above-described basic configuration. Specifically, in each of toners TA-1 to TA-12, the toner particles include silica particles and resin particles as external additives. The resin particles were substantially composed of a styrene-acrylic acid resin. The toner base particles were provided with a toner core and a shell layer covering the surface of the toner core. The toner core contained a binder resin (three kinds of polyester resins having different softening points) and a release agent (carnauba wax). The shell layer covered an area of 60% to 80% of the surface area of the toner core (see “Shell Coverage” in Table 2). The amount of silica particles was 1.0 to 2.0 parts by mass and the amount of resin particles was 0.5 to 2.0 parts by mass with respect to 100 parts by mass of toner base particles. (See “Amount” in “External Conditions” in Table 1). Release agent (contained in toner core) measured by quantitative analysis by Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) in the range from the toner particle surface to a depth of 1 nm The number of fragment ions derived from carnauba wax) was 1000 ppm or more and 2000 ppm or less with respect to the count number of all positive ions (see “release amount (surface layer part)” in Table 2). The silica liberation rate of the toner measured after the airflow classification process under the conditions of a toner supply amount of 100 g / min, a rotation speed of 12000 rpm, and a blower air volume of 6 m ³ / min was 3.0% to 5.0% (Table) 2 (refer to “silica liberation rate”).

  As shown in Table 3, each of the toners TA-1 to TA-12 was excellent in all of the charge amount, charge stability, heat resistant storage stability, adhesion resistance, cleaning property, and developability. When continuous printing is performed using any of the toners TA-1 to TA-12, high-quality images can be continuously formed over a long period of time while suppressing the occurrence of sleeve fixation and blade turning. It was.

  The toner for developing an electrostatic latent image according to the present invention can be used to form an image in, for example, a copying machine, a printer, or a multifunction machine.

Claims (6)

An electrostatic latent image developing toner comprising a plurality of toner particles comprising toner mother particles and an external additive attached to the surface of the toner mother particles,
The toner particles include silica particles and resin particles as the external additive,
The resin particles are substantially composed of a styrene-acrylic acid resin,
The toner base particles include a core containing a binder resin and a release agent, and a shell layer covering the surface of the core,
The shell layer covers an area of 60% to 80% of the surface area of the core,
The amount of the silica particles is 1.0 to 2.0 parts by mass with respect to 100 parts by mass of the toner base particles, and the amount of the resin particles is 0.5 to 2.0 parts by mass. And
In the range from the surface of the toner particle to a depth of 1 nm, the number of fragment ions derived from the release agent measured by quantitative analysis by time-of-flight secondary ion mass spectrometry is the count of all positive ions. 1000 ppm to 2000 ppm with respect to the number,
An electrostatic latent image having a silica liberation rate of 3.0% or more and 5.0% or less measured after airflow classification with a toner supply rate of 100 g / min, a rotation speed of 12000 rpm, and a blower airflow rate of 6 m ³ / min. Developing toner.   The number average primary particle diameter of the silica particles is 0.01 μm or more and 0.10 μm or less, and the number average primary particle diameter of the resin particles is 0.05 μm or more and 0.20 μm or less. Toner for electrostatic latent image development.   The toner for developing an electrostatic latent image according to claim 1, wherein the shell layer has a thickness of 30 nm to 60 nm.   The electrostatic shell image developing toner according to claim 1, wherein the shell layer contains a copolymer of at least one styrene monomer and at least one acrylic monomer. .   The shell layer contains a resin having one or more alcoholic hydroxyl groups derived from 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate. The electrostatic latent image developing toner according to claim 1.   6. The electrostatic latent image developing toner according to claim 1, wherein the core contains a plurality of types of polyester resins having different softening points as the binder resin. 7.